THE doctrine of the inheritance of acquired characters is by no means so dead as its opponents thought a generation ago. The effects of Weismann's knockout blow are wearing off, and the heart begins to throb again, somewhat irregularly, but gaining strength all the time. In his Royal Institution Discourse of June 5, on “Habit: The Driving Factor in Evolution”, printed in a special supplement this week, Prof. E. W, MacBride takes a strong stand on the side of the heriiability of acquired characters. Dissatisfied with the evidence formerly adduced for the occurrence of evolution, he re-examines the question along three lines which he regards as the only possible approaches. These are: the line of racial differentiation amongst animals at the present day, the line of fossil evidences of past specific changes, and the line of embryonic and larval development. And each of these lines, traced to its end, leads Prof. MacBride to the conclusion, which would have delighted Lamarck as it will shock many adherents of orthodoxy, that habit or change of habit is at the bottom of the changes of structure which represent the difference between one species and another. The interesting examples cited in support of the thesis will be eagerly scanned, but whether all of them will satisfy the doubters is another question.